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FILE(1)								       FILE(1)

NAME
       file - determine file type

SYNOPSIS
       file [ -bcikLnNsvz ] [ -f namefile ] [ -F separator ] [ -m magicfiles ]
       file ...
       file -C [ -m magicfile ]

DESCRIPTION
       This manual page documents version 4.02 of the file command.

       File tests each argument in an attempt to classify it.  There are three
       sets  of tests, performed in this order: filesystem tests, magic number
       tests, and language tests.  The first test  that	 succeeds  causes  the
       file type to be printed.

       The  type  printed will usually contain one of the words text (the file
       contains only printing characters and a few common  control  characters
       and  is	probably  safe	to read on an ASCII terminal), executable (the
       file contains the result of compiling a program in a  form  understand‐
       able  to	 some  UNIX  kernel or another), or data meaning anything else
       (data is usually `binary' or non-printable).  Exceptions are well-known
       file  formats  (core  files,  tar  archives)  that are known to contain
       binary data.  When modifying the file /usr/share/file/magic or the pro‐
       gram  itself,  preserve these keywords .	 People depend on knowing that
       all the readable files in a directory have the word  ``text''  printed.
       Don't  do as Berkeley did and change ``shell commands text'' to ``shell
       script''.  Note that the file /usr/share/file/magic is  built  mechani‐
       cally  from a large number of small files in the subdirectory Magdir in
       the source distribution of this program.

       The filesystem tests are based on examining the return from  a  stat(2)
       system  call.   The  program  checks to see if the file is empty, or if
       it's some sort of special file.	Any known file	types  appropriate  to
       the  system you are running on (sockets, symbolic links, or named pipes
       (FIFOs) on those systems that implement them) are intuited if they  are
       defined in the system header file <sys/stat.h>.

       The magic number tests are used to check for files with data in partic‐
       ular fixed formats.  The canonical example of this  is  a  binary  exe‐
       cutable	(compiled  program)  a.out  file,  whose  format is defined in
       a.out.h and possibly exec.h in the standard include  directory.	 These
       files  have  a  `magic  number'	stored	in a particular place near the
       beginning of the file that tells the UNIX  operating  system  that  the
       file  is	 a binary executable, and which of several types thereof.  The
       concept of `magic number' has been applied by extension to data	files.
       Any  file  with	some invariant identifier at a small fixed offset into
       the file can usually be described in this way.  The information identi‐
       fying   these   files   is   read   from	  the	compiled   magic  file
       /usr/share/file/magic.mgc , or  /usr/share/file/magic  if  the  compile
       file does not exist.

       If  a  file  does not match any of the entries in the magic file, it is
       examined to see if it seems to be a text file.  ASCII, ISO-8859-x, non-
       ISO  8-bit  extended-ASCII character sets (such as those used on Macin‐
       tosh and IBM PC systems), UTF-8-encoded	Unicode,  UTF-16-encoded  Uni‐
       code,  and  EBCDIC character sets can be distinguished by the different
       ranges and sequences of bytes that constitute printable	text  in  each
       set.   If  a  file  passes  any	of  these  tests, its character set is
       reported.  ASCII, ISO-8859-x, UTF-8, and extended-ASCII files are iden‐
       tified  as  ``text'' because they will be mostly readable on nearly any
       terminal; UTF-16 and EBCDIC are only ``character data'' because,	 while
       they  contain  text, it is text that will require translation before it
       can be read.  In addition, file will attempt to determine other charac‐
       teristics of text-type files.  If the lines of a file are terminated by
       CR, CRLF, or NEL,  instead  of  the  Unix-standard  LF,	this  will  be
       reported.  Files that contain embedded escape sequences or overstriking
       will also be identified.

       Once file has determined the character set used in a text-type file, it
       will  attempt  to  determine in what language the file is written.  The
       language tests look for particular strings (cf names.h) that can appear
       anywhere	 in  the first few blocks of a file.  For example, the keyword
       .br indicates that the file is most likely a troff(1) input file,  just
       as  the	keyword	 struct	 indicates  a C program.  These tests are less
       reliable than the previous two groups, so they are performed last.  The
       language	 test  routines	 also test for some miscellany (such as tar(1)
       archives).

       Any file that cannot be identified as having been written in any of the
       character sets listed above is simply said to be ``data''.

OPTIONS
       -b      Do not prepend filenames to output lines (brief mode).

       -c      Cause a checking printout of the parsed form of the magic file.
	       This is usually used in conjunction with	 -m  to	 debug	a  new
	       magic file before installing it.

       -C      Write  a	 magic.mgc output file that contains a pre-parsed ver‐
	       sion of file.

       -f namefile
	       Read the names of the files to be examined from	namefile  (one
	       per  line)  before  the	argument  list.	 Either namefile or at
	       least one filename argument must be present; to test the	 stan‐
	       dard input, use ``-'' as a filename argument.

       -F separator
	       Use  the specified string as the separator between the filename
	       and the file result returned. Defaults to ``:''.

       -i      Causes the file command to output mime type strings rather than
	       the  more  traditional  human  readable	ones.  Thus it may say
	       ``text/plain; charset=us-ascii'' rather	than  ``ASCII  text''.
	       In  order for this option to work, file changes the way it han‐
	       dles files recognised by the command itself (such  as  many  of
	       the  text  file	types,	directories  etc), and makes use of an
	       alternative ``magic'' file.  (See ``FILES'' section, below).

       -k      Don't stop at the first match, keep going.

       -L      option causes symlinks to be followed, as the like-named option
	       in ls(1).  (on systems that support symbolic links).

       -m list Specify	an  alternate  list of files containing magic numbers.
	       This can be a single file, or a colon-separated list of files.

       -n      Force stdout to be flushed after checking each file.   This  is
	       only  useful if checking a list of files.  It is intended to be
	       used by programs that want filetype output from a pipe.

       -N      Don't pad filenames so that they align in the output.

       -s      Normally, file only attempts to read and determine the type  of
	       argument	 files which stat(2) reports are ordinary files.  This
	       prevents problems, because reading special files may have pecu‐
	       liar  consequences.   Specifying	 the  -s option causes file to
	       also read argument files which are block or  character  special
	       files.	This is useful for determining the filesystem types of
	       the data in raw disk partitions, which are block special files.
	       This  option  also  causes  file	 to disregard the file size as
	       reported by stat(2) since on some systems  it  reports  a  zero
	       size for raw disk partitions.

       -v      Print the version of the program and exit.

       -z      Try to look inside compressed files.

FILES
       /usr/share/file/magic.mgc - default compiled list of magic numbers

       /usr/share/file/magic - default list of magic numbers

       /usr/share/file/magic.mime.mgc  -  default  compiled list of magic num‐
       bers, used to output mime types when the -i option is specified.

       /usr/share/file/magic.mime - default list of  magic  numbers,  used  to
       output mime types when the -i option is specified.

ENVIRONMENT
       The  environment	 variable  MAGIC  can be used to set the default magic
       number files.

SEE ALSO
       magic(5) - description of magic file format.
       strings(1), od(1), hexdump(1) - tools for examining non-textfiles.

STANDARDS CONFORMANCE
       This program is believed to exceed the System V Interface Definition of
       FILE(CMD),  as  near  as one can determine from the vague language con‐
       tained therein.	Its behaviour is mostly compatible with the  System  V
       program	of  the same name.  This version knows more magic, however, so
       it will produce different (albeit more accurate) output in many cases.

       The one significant difference between this version  and	 System	 V  is
       that this version treats any white space as a delimiter, so that spaces
       in pattern strings must be escaped.  For example,
       >10  string    language impress	  (imPRESS data)
       in an existing magic file would have to be changed to
       >10  string    language\ impress	  (imPRESS data)
       In addition, in this version, if a pattern string contains a backslash,
       it must be escaped.  For example
       0    string	   \begindata	  Andrew Toolkit document
       in an existing magic file would have to be changed to
       0    string	   \\begindata	  Andrew Toolkit document

       SunOS  releases	3.2  and later from Sun Microsystems include a file(1)
       command derived from the System V one, but with	some  extensions.   My
       version	differs from Sun's only in minor ways.	It includes the exten‐
       sion of the `&' operator, used as, for example,
       >16  long&0x7fffffff	>0	  not stripped

MAGIC DIRECTORY
       The magic file entries have been collected from various sources, mainly
       USENET,	and  contributed by various authors.  Christos Zoulas (address
       below) will collect additional or corrected magic file entries.	A con‐
       solidation of magic file entries will be distributed periodically.

       The  order  of  entries in the magic file is significant.  Depending on
       what system you are using, the order that they are put together may  be
       incorrect.   If	your  old file command uses a magic file, keep the old
       magic   file   around   for   comparison	  purposes   (rename   it   to
       /usr/share/file/magic.orig).

EXAMPLES
       $ file file.c file /dev/{wd0a,hda}
       file.c:	 C program text
       file:	 ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
		 dynamically linked (uses shared libs), stripped
       /dev/wd0a: block special (0/0)
       /dev/hda: block special (3/0)
       $ file -s /dev/wd0{b,d}
       /dev/wd0b: data
       /dev/wd0d: x86 boot sector
       $ file -s /dev/hda{,1,2,3,4,5,6,7,8,9,10}
       /dev/hda:   x86 boot sector
       /dev/hda1:  Linux/i386 ext2 filesystem
       /dev/hda2:  x86 boot sector
       /dev/hda3:  x86 boot sector, extended partition table
       /dev/hda4:  Linux/i386 ext2 filesystem
       /dev/hda5:  Linux/i386 swap file
       /dev/hda6:  Linux/i386 swap file
       /dev/hda7:  Linux/i386 swap file
       /dev/hda8:  Linux/i386 swap file
       /dev/hda9:  empty
       /dev/hda10: empty

       $ file -i file.c file /dev/{wd0a,hda}
       file.c:	    text/x-c
       file:	    application/x-executable, dynamically linked (uses shared libs),
       not stripped
       /dev/hda:    application/x-not-regular-file
       /dev/wd0a:   application/x-not-regular-file

HISTORY
       There  has  been	 a  file command in every UNIX since at least Research
       Version 4 (man page dated November, 1973).  The System V version intro‐
       duced  one  significant major change: the external list of magic number
       types.  This slowed the program down slightly but made it  a  lot  more
       flexible.

       This  program, based on the System V version, was written by Ian Darwin
       <ian@darwinsys.com> without looking at anybody else's source code.

       John Gilmore revised the code extensively, making it  better  than  the
       first  version.	 Geoff Collyer found several inadequacies and provided
       some magic file entries.	 Contributions by  the	`&'  operator  by  Rob
       McMahon, cudcv@warwick.ac.uk, 1989.

       Guy Harris, guy@netapp.com, made many changes from 1993 to the present.

       Primary	development and maintenance from 1990 to the present by Chris‐
       tos Zoulas (christos@astron.com).

       Altered by Chris Lowth, chris@lowth.com, 2000: Handle the ``-i'' option
       to  output  mime	 type  strings and using an alternative magic file and
       internal logic.

       Altered by Eric Fischer (enf@pobox.com), July, 2000, to identify	 char‐
       acter codes and attempt to identify the languages of non-ASCII files.

       The  list  of  contributors  to	the "Magdir" directory (source for the
       /etc/magic file) is too long to include here.  You know	who  you  are;
       thank you.

LEGAL NOTICE
       Copyright  (c)  Ian  F. Darwin, Toronto, Canada, 1986-1999.  Covered by
       the standard Berkeley Software Distribution  copyright;	see  the  file
       LEGAL.NOTICE in the source distribution.

       The files tar.h and is_tar.c were written by John Gilmore from his pub‐
       lic-domain tar program, and are not covered by the above license.

BUGS
       There must be a better way to automate the construction	of  the	 Magic
       file  from  all the glop in magdir.  What is it?	 Better yet, the magic
       file should be compiled into  binary  (say,  ndbm(3)  or,  better  yet,
       fixed-length  ASCII  strings  for  use in heterogenous network environ‐
       ments) for faster startup.  Then the program would run as fast  as  the
       Version	7 program of the same name, with the flexibility of the System
       V version.

       File uses several algorithms that favor speed over  accuracy,  thus  it
       can be misled about the contents of text files.

       The  support  for  text	files (primarily for programming languages) is
       simplistic, inefficient and requires recompilation to update.

       There should be an ``else'' clause to follow a series  of  continuation
       lines.

       The  magic  file	 and  keywords should have regular expression support.
       Their use of ASCII TAB as a field delimiter is ugly and makes  it  hard
       to edit the files, but is entrenched.

       It might be advisable to allow upper-case letters in keywords for e.g.,
       troff(1) commands vs man page macros.  Regular expression support would
       make this easy.

       The  program doesn't grok FORTRAN.  It should be able to figure FORTRAN
       by seeing some keywords which appear indented at	 the  start  of	 line.
       Regular expression support would make this easy.

       The  list  of  keywords in ascmagic probably belongs in the Magic file.
       This could be done by using some keyword like `*' for the offset value.

       Another optimisation would be to sort the magic file  so	 that  we  can
       just run down all the tests for the first byte, first word, first long,
       etc, once we have fetched it.  Complain about conflicts	in  the	 magic
       file  entries.	Make  a rule that the magic entries sort based on file
       offset rather than position within the magic file?

       The program should provide a way to give an estimate of ``how good''  a
       guess  is.  We end up removing guesses (e.g. ``From '' as first 5 chars
       of file) because they are not as good as other  guesses	(e.g.  ``News‐
       groups:''  versus  ``Return-Path:'').   Still,  if the others don't pan
       out, it should be possible to use the first guess.

       This program is slower than some vendors' file commands.	 The new  sup‐
       port for multiple character codes makes it even slower.

       This manual page, and particularly this section, is too long.

AVAILABILITY
       You can obtain the original author's latest version by anonymous FTP on
       ftp.astron.com in the directory /pub/file/file-X.YZ.tar.gz

			  Copyright but distributable		       FILE(1)
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